The main objective of this ongoing project is the systematic investigation of the anatomy, physiology and effects of pathological lesions of the vestibulo-ocular system. The studies are being conducted in normal and labyrinthectomized cats and rabbits. A comprehensive study is to be conducted of the characteristics of the eye movements during physiological stimulation of the labyrinthine receptors with the purpose of identifying the origin, either the semicircular canals or maculae, of the vestibulo-oculomotor reflexes. A quantitative study will be made of changes in neural activity in single isolated fibers of the III, IV and VI cranial nerves to investigate the intrinsic mechanism of production of eye movements, particularly those during nystagmus. Computer programs are being used and will continue to be developed for quantitative measurements, graphical display and correlative study of the results of the above projects.